Adhesive sheet, metal-laminated sheet and printed wiring board

Abstract

The adhesive sheet contains a substrate film and an adhesive layer formed at least on one surface of the substrate film. The substrate film is made of a polyimide film showing a degree of curl after a heat treatment at 300° C. of not more than 10%. The adhesive sheet of the present invention can be used for electronic parts and the like exposed to high temperature particularly because warpage and distortion thereof caused by a high temperature treatment are suppressed, and can improve quality and yield of electronic parts and the like.

Description

REFERENCE TO RELATED APPLICATIONS[0001]This application is a national stage application under 35 USC 371 of International Application No. PCT / JP2005 / 012624, filed Jul. 1, 2005, which claims the priority of Japanese Applications Nos. 2005-122566, 2005-122567, 2005-122568 and 2005-122569, each filed on Apr. 20, 2005. The contents of the International Applications and the prior Japanese applications are herein incorporated by reference.FIELD OF THE INVENTION[0002]The present invention relates to an adhesive sheet, a metal-laminated sheet and a printed circuit board. More particularly, the present invention relates to an adhesive sheet used for forming an insulating layer for a printed circuit board and the like to be used for a flexible printed circuit substrate and the like aiming at down-sizing and reducing weight of electronic devices and electronic parts, a metal-laminated sheet wherein a metal foil is laminated on the adhesive sheet and a printed circuit board obtained by processi...

AI Technical Summary

Benefits of technology

[0127]As long as the advantage of the present invention is not impaired, a thermosetting adhesive, for example, an epoxy or cyanate adhesive, may be mixed with the thermoplastic adhesive of the present invention, and the proportion of the thermosetting adhesive is 40 mass % at most relative to the total mass of the adhesive composition constituting the adhesive layer.

[0128]The aforementioned thermoplastic polyimide resin can be produced by reacting the aforementioned respective components, and further, when the case demands, other tetracarboxylic acid dianhydride and other diamine, in an organic solvent, at a temperature not more than about 100° C., particularly 20° C.-60° C., to give a polyamic acid solution, and using this polyamic acid solution as a dope solution.

[0129]In addition, a solution of a thermocompression bonding polyimide resin in an organic solvent can be obtained by affording a powder by heating a solution of polyamic acid produced as mentioned above to 150-250° C., or adding an imidating agent to allow reaction at a temperature of 150° C. or below, particularly 15-50° C., to perform imide cyclization and evaporating the solvent, or precipitation in a poor solvent, and dissolving the powder in an organic solution.

[0130]To obtain a thermoplastic polyimide resin in the present invention, respective components are preferably reacted in the aforementioned organic solvent in proportions such that the ratio of the amount of diamine used (the number of moles of amino group) to the total number of moles of acid anhydride (total mol of acid anhydride group of tetraacid dianhydride and dicarboxylic acid anhydride) is preferably 0.92-1.1, particularly 0.98-1.1, especially 0.99-1.1, and the ratio of the amount of dicarboxylic acid anhydride used to the number of moles of acid anhydride group of tetracarboxylic acid dianhydride is preferably not more than 0.05, particularly not more than 0.02.

[0131]When the proportion of the aforementioned diamine and dicarboxylic acid anhydride used is outside the aforementioned range, the obtained polyamic acid and thermoplastic polyimide obtained by imidating same have small molecular weights, which in turn decreases the adhesion strength of the flexible metal foil laminate. For the purpose of suppressing gelling of polyamic acid, a phosphorus stabilizer, for example, triphenyl phosphite, triphenyl phosphate and the like can be added within the range of 0.01-1 mass % relative to the solid (polymer) concentration during polymerization of polyamic acid. For the purpose of promoting imidation, a basic organic compound catalyst can be added to a dope solution.

[0132]For example, imidazole, 2-imidazole, 1,2-dimethylimidazole, 2-phenylimidazole and the like can be used in a proportion of 0.05-10 mass %, particularly 0.1-2 mass %, relative to polyamic acid. They are used to avoid insufficient imidation because a polyimide film is formed at a comparatively low temperature. For the purpose of stabilizing the adhesion strength, an organic aluminum compound, an inorganic aluminum compound or an organotin compound may be added to a thermocompression bonding polyimide starting material dope. For example, aluminum hydroxide, aluminum triacetylacetonate and the like can be added in a proportion of not less than 1 ppm, particularly 1-1000 ppm, as an aluminum metal relative to polyamic acid.

Problems solved by technology

Conventionally known substrate films made of a polyimide film or a polyimide benzoxazole film are inferior in heat resistance as compared to substrates made of ceramic.

In addition, they have problem of easy occurrence of warpage and distortion during production of electronic parts due to property variation within the film.

However, even if apparent film warpage, namely, exteriorized film warpage etc., could be eliminated, the problem of potential distortion that could be exteriorized by a treatment at a high temperature to cause curling, which treatment is particularly necessary for high temperature processing for the application of electronic parts, has not been solved.

Accordingly, even if a film shows small apparent warpage, if it permits curling during processing, the yield of production decreases and high quality electronic parts are often difficult to obtain.

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